1. Weathering: This is the initial stage where rocks are broken down into smaller pieces. It happens through two main ways:
* Physical weathering: This involves mechanical forces like:
* Frost wedging: Water seeps into cracks, freezes and expands, breaking the rock.
* Abrasion: Rocks rub against each other, causing them to wear down.
* Thermal stress: Repeated heating and cooling can cause rocks to crack.
* Chemical weathering: This involves chemical reactions that break down rocks, such as:
* Dissolution: Rocks dissolve in acidic water.
* Oxidation: Minerals in rocks react with oxygen, changing their composition.
* Hydrolysis: Water reacts with minerals in rocks, creating new minerals.
2. Erosion: Once weathered, the rock fragments are picked up and carried away by agents like:
* Water: Rivers, streams, waves, and rain all carry sediment.
* Wind: Wind can transport sand, dust, and even small pebbles.
* Ice: Glaciers carve out valleys and transport large amounts of rock.
* Gravity: Landslides and rockfalls move sediment downhill.
3. Transportation: The eroded sediments are carried by the agents of erosion, often traveling long distances. During transportation, the sediments may be further broken down and sorted by size.
4. Deposition: Eventually, the transporting agent loses energy and the sediments settle out, or are deposited. This happens in various environments:
* Riverbeds: Rivers deposit sediment as their flow slows down.
* Oceans: Waves and currents carry sediment into the ocean, where it settles on the seabed.
* Lakes: Lakes can trap sediment from rivers and other sources.
* Deserts: Wind deposits sand in dunes and other landforms.
* Glacial valleys: Glaciers deposit sediment when they melt.
Types of Sediments:
* Clastic sediments: These are rock fragments broken down from other rocks (e.g., sand, silt, clay).
* Chemical sediments: These form from precipitation of minerals from water (e.g., limestone, rock salt).
* Biogenic sediments: These are made up of the remains of organisms (e.g., shells, coral reefs).
Sedimentary Rocks:
Over time, deposited sediments are buried, compacted, and cemented together to form sedimentary rocks. These rocks provide valuable clues about the Earth's history and past environments.
